1. Technical Field
The present invention relates in general to storage devices, in particular, to an improved system, method and apparatus for a storage device with adaptive error-correcting codes for improved areal efficiency of a magnetic hard disk.
2. Description of the Related Art
There is increasingly difficulty to increase the areal density of hard disk drive storage devices, due to the challenges of improving the performance of components (media, head, and channel) associated with recording at smaller recording geometries. This is the case for perpendicular, discrete-tract media, patterned, and thermal-assisted record recording systems. At the same time, methods must be provided to strengthen data robustness and guard against thermal decay of the data. Thermal decay is especially serious in bit-patterned media where each island stores a channel bit. What is needed is a method to continue to lower the probability of accumulating written-in channel bit errors which over time may be exacerbated by thermal decay and ultimately may exceed the capability of a modestly-sized error-correcting code (ECC). Brute-force pathways of adding more and more ECC are available in principle. But, they come at the expense of lower user-bit density.
In continuous granular media, scaling of grain sizes has become increasingly difficult. As a consequence, the number of grains per bit has been decreasing. This implies that the intrinsic media signal-to-noise ratio (SNR) has been diminishing. Extending continuous granular media may therefore be predicated on the ability to operate in lower SNR environments than is currently customary. Given that reduction of fabrication tolerances of bit-patterned media manufacture is entailing considerable expense, in order to reduce the expense, a higher percentage of written-in errors during initial write may be accepted in certain circumstances. Locally, at a certain period of time, there may be a very strong and expensive ECC applied. During the initial write, a strong ECC may be needed in order to guarantee the recovery of the user-bits.